The present invention relates to a process for preparing Masa flour from dry milled maize and to a novel device suitable for (but not limited to) carrying out certain steps in the process.
Masa dough is traditionally manufactured by steeping whole grain maize in hot water in the presence of a low percentage of added lime (calcium hydroxide). The resultant softened kernels are milled down to form a dough from which tortilla (corn chips) can be sheeted and fried. The precise degree of gelatinisation of the starch within the grain is important in achieving a coherent dough and the addition of lime contributes to the flavour and texture of the corn chip.
The traditional process is known technically as nixtamilisation and has two inherent drawbacks for widespread commercial use. Firstly, the process generates substantial volumes of liquid effluent containing between 2 and 6% dissolved and suspended solids. Secondly, the Masa dough has to be used immediately to avoid deterioration and mould growth. Consequently, the dough has to be dried and ground down to a meal in order to facilitate off-site distribution to customers. This is an inefficient, energy intensive process which is reflected in the cost of the final product. Although various extrusion techniques have been described, none have yet yielded products which match the flavour, texture and functionality of the products of traditional nixtamilisation.
Most modern snack factories in Europe use dry Masa flour as a raw material. Masa flour imported from the US or South Africa attracts a substantial tariff under the European CAP regime and consequently represents an expensive raw material for the European snack food manufacturer in comparison to native cereals. There is an incentive for the European maize miller to develop a process that uses indigenous varieties of maize.
Thus there is a need for an improved commercial process which is versatile in the sense that it can be used with a variety of maize types. The present invention seeks to fulfil this need by replacing the steeping of whole grain with continuous counter-current cooking of dry milled maize meal with live steam.
Thus viewed from one aspect the present invention provides a process for preparing Masa flour from maize comprising:
dry milling the maize to obtain a dry milled maize meal;
blending the dry milled maize meal with hot water and lime to obtain a blended meal;
exposing the blended meal to live steam in a heated cooking vessel; and
drying and cooling the steam-treated, blended meal.
The term xe2x80x9clive steamxe2x80x9d is used herein to describe direct contact of steam with the blended meal (ie in comparison to indirect contact where steam heats a cooking vessel or heat exchanger which is in contact with the blended meal).
The versatility of the invention is such that dry milling may be advantageously carried out on a variety of types of grain and irrespective of the precise flow of the dry milling equipment.